The present invention is directed to methods of tuning optical properties of organic material containing integrated optical waveguide devices. More particularly, the present invention is directed to wavelength tuning of passively athermalized wavelength division multiplexer or demultiplexer devices, more particularly of phased array (phasar) devices, by exposing the organic material to radiation such as UV light. More specifically, the organic material contained in the phasars either is used as an overclad, or fills a triangular groove made in the optical path of the phasar.
The channel center wavelengths (called hereafter channel wavelengths) of optical waveguide multiplexers and demultiplexers must be adjusted to the ITU-T wavelength grid for wavelength division multiplexer (WDM) components. In the case of phased array multiplexers and demultiplexers (phasars), in order to adjust the wavelengths to within 0.01 nm, a reproducibility of 10xe2x88x925 on the effective index is required. In practice, this reproducibility is very difficult to obtain. Thus, the wavelengths are usually adjusted to the ITU-T grid by tuning the device temperature, if the device is temperature sensitive. The channel wavelengths of silica-based phasars are sensitive to temperature because of the temperature-dependent refractive index of silicate glasses. This problem is usually overcome by maintaining the device at a constant temperature (active athermalization). The channel wavelengths can, thus, be finely tuned by controlling the device temperature (1xc2x0 C.=0.01 nm for silicate glass devices).
If necessary, a rough tuning can be performed before the fine tuning. It is well known to the skilled artisan that shifting the input and/or output port(s) enables shifting of the channel wavelengths, as described in, for example, Lin et al., IEEE Photonics Technol. Lett., 1996, 8, 1501-1503, which is incorporated herein by reference in its entirety. For example, shifting the output ports of a phased array demultiplexer by one port results in shifting the channel wavelengths by one channel spacing. This tuning, however, is made in discrete steps and usually has to be completed by a fine tuning, for example, by tuning the device temperature as described above or, alternatively, by the method of the invention.
On the other hand, if the process reproducibility is sufficient (typically, 0.2 nm in wavelength can be expected), only a fine tuning is required. The fine tuning can be made by tuning the device temperature as described above or, alternatively, by the method of the invention.
Active athermalization requires power consumption and temperature control. Accordingly, passively athermalized devices are currently being developed. Passive athermalization suppresses the temperature sensitivity of the devices, and, thus, suppresses the possibility of finely tuning the channel wavelengths by using the temperature of the device. Thus, methods of tuning wavelengths in passively athermalized devices are desired. Accordingly, the present invention is directed to novel methods of wavelength tuning for athermalized devices, in particular for athermalized phasars.
The present invention is directed to novel methods of wavelength tuning of an athermalized wavelength division multiplexer or demultiplexer device comprising inserting a triangular groove filled with organic material in the optical path and exposing the organic material to radiation such as UV light.
The present invention is also directed to a method of wavelength tuning of an athermalized wavelength division multiplexer or demultiplexer device comprising using an organic material as an overclad and exposing the organic material to radiation such as UV light.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.